1. Field of the Invention
The present invention relates to azo dyes and azo-metal complexes for atomic force microscope (AFM) lithography, and more specifically to xcfx80-conjugated azo dyes and azo-metal complexes having both electron-donating and electron-accepting groups within molecules, so that fine patterns of nanometer-scale order can be formed on silicon and metal substrates by AFM.
2. Description of the Prior Art
The trend of downsizing has been in rapid progress in the field of electronic engineering. This trend is easily identified in data processing, communication and various appliance industries. From the view of IT (information technology) industry, it can be said that an era of sub-micro technology has come passing the era of micro technology. With this downsizing trend, the optical micro-processing technology in microelectronics enabled ultra-integration up to 0.1 xcexcm of line-width in 1996 since the appearance of 4K DRAM in the 1970s.
Because excimer laser, X-ray, electron beam and focused ion beam technologies are expected to be the micro-processing that enables the sub-micrometer resolution technology, the advanced countries are strategically developing these next-generation micro-processing technologies.
As the electron beam micro-processing technology is emerging as a powerful tool for processing ultra-micro devices of below 0.1 xcexcm order, a new type of ideal molecular film resist, which can overcome the limit of the conventional photoresist, is required. Currently, the electron beam resist is widely used in production of masks for micro processing. But, it is not directly used in processing semiconductor devices. However, with the development of ultramicro-processing equipments and improvement of resist capacities, the probability of using electron beam resist is on the increase. Therefore, we carried out basic researches on ultramicro pattern forming using AFM, which is emerging as a new micro-processing technology.
Generally, atomic force microscope is used in morphology study of solid sample surfaces without damaging it. Nanolithography is recognized as a powerful method to visualize the fabrication of nanoelectronic devices these days. Among several techniques, lithographic methods using AFM are promising techniques to produce nano-sized patterns. One of them is AFM anodization lithography based on an electrochemical reaction on the surface of metal or semiconductor.
This technique can be used to control materials at nano level, by producing artificial nano structures. Currently, the level of below 30 nm cannot be easily accessed by the conventional techniques including the e-beam lithography, and AFM can be said as an unparalleled technique in this field.
In the nano lithography using AFM, a variety of methods, including ultramicro pattern formation using resist material and oxide pattern formation on hydrogen passivated Si-wafer or poly-Si surface by applying electric field using AFM tip, are being carried out. Also, this technique can be applied to the next-generation data storage system when combined with electrostatic force microscopy (EFM) and scanning capacitance microscopy (SCM).
In most conventional AFM lithography techniques, the pattern formation was carried out by preparing self-assembled monolayer film using organic resist (Jpn. J. Appl. Phys., 37, 7148, Kim J. C.; J. Kor. Phys. Soc., 35, 1013, 1999, Kim, J. C.; Adv. Mater., 12, 6, 424, 2000, Rivka M.). However, because the chemical bonding of the molecules to the substrate, it is rather difficult to remove the molecular film completely. Because the present invention forms the film by spin coating rather than chemical bonding, a thin and uniform film is obtained and it can be easily removed after patterning.
Important factors in the AFM lithography are applied voltage, current, scanning speed, humidity and physical properties of resist, etc. (J. Appl. Phys. Lett., 2592, 2002, Sang Jung A.; Vac. Sci. Technol., 1223, 1996, Sugimura, A.; J. Vac. Sci. Technol., 2912, 1997, Birkelund K.; J. Appl. Phys. Lett., 285, 1997, Avouris P.).
If the processing condition is improper, the line-width becomes non-uniform and the line can be broken during patterning. Therefore, development of high-performance resist and proper control of applied voltage, scanning speed and humidity are required for better pattern formation.
In the present invention, ultra-thin resist of sub-nanometer order is formed on the substrate using a spin coater, and a pattern with minimum line-width smaller than 35 nm is prepared. If this resist material is used in the optimum processing condition, ultra-micro pattern of nanometer order can be obtained. This technique can be a very important basic technique in the development of proto-type terabit semiconductor memory devices in the near future.
The present invention forms thin film of xcfx80-conjugated organic materials having both electron-donating and electron-accepting groups on the metal substrate, not by chemical bonding but by spin coating. Therefore, a thin and uniform film is obtained and it can be easily removed after patterning. The resist material of the present invention can be used in ultra-thin film patterning using AFM lithography at the optimum condition. This technique can be a very important basic technique in the development of proto-type terabit semiconductor memory devices.